The Fischer-Tropsch technology is known in literature, for preparing hydrocarbons from mixtures of gas based on hydrogen and carbon monoxide, conventionally known as synthesis gas. A document which summarizes the main works on the Fischer-Tropsch synthesis reaction is represented by Sie and Krishna, Appl. Catalysis A: General (1999), 186, 55-70.
The Fischer-Tropsch technology is typically based on the use of slurry reactors, reactors which are normally used in relation to chemical reactions which are carried out in multiphase systems in which a gaseous phase is bubbled into a suspension of a solid in a liquid. In the case of Fischer-Tropsch, the gaseous phase consists of synthesis gas, with a molar ratio H2/CO ranging from 1 to 3, the liquid phase, at the reaction temperature, prevalently consists of the reaction product, i.e. essentially linear hydrocarbons with a high number of carbon atoms, and the solid phase is prevalently represented by the catalyst.
The Fischer-Tropsch reaction is an exothermic reaction which, for its industrial embodiment, requires internal heat exchanger devices, for removing the heat produced and for controlling the thermal profile inside the reactor.
The objective of the present invention is the running of the phases which are not included in the normal operating conditions for Fischer-Tropsch reactions and which are particularly critical for the catalyst performances, such as for example:                charging;        start-up/conditioning;        make-up (subsequent additions of catalyst);        temporary or definite shut-down of the reaction section;        re-start-up after the temporary shut-down.        
In scientific literature, for example in published Australian patent application AU 200066518 A1, a process is described for treating, in the charging phase, a catalyst for Fischer-Tropsch reactions which are carried in fluidized multiphase reactors and for running these during the shut-down or re-start-up phases.